This article explores the possibility that there is a parental duty to use preimplantation genetic diagnosis (PGD) for the medical benefit of future children. Using one genetic disorder as a paradigmatic example, we find that such a duty can be supported in some situations on both ethical and legal grounds. Our analysis shows that an ethical case in favor of this position can be made when potential parents are aware that a possible future child is at substantial risk of inheriting a serious genetic condition. We further argue that a legal case for a duty to use PGD for medical benefit can be made in situations in which potential parents have chosen to conceive through in vitro fertilization and know that any children conceived are at substantial risk of having a serious genetic condition.